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Problematic Port Negotiation Mode Results in Unidirectional Communication of Links

Publication Date:  2012-07-27 Views:  32 Downloads:  0
Issue Description
Version: V300R001C01B052
Networking diagram: NE40E (GE1/0/4)-R (Router of C company)
After the NE40E is upgraded from v300r001b02msp03 to V300R001C01B052, GE1/0/4 is up, but its peer is down. 
            
Alarm Information
Null
            
Handling Process
1. Check the information of GE1/0/4 of NE40E, and the interface is up; however, there is only outbound traffic, without the inbound traffic yet. 
2. Check the interface at peer, and it is down.
3. Change the manual setting of the interface to auto-negotiation, and the problem is solved. 
            
Root Cause
1. Unidirectional communication occurs to the links, and it results in the static black hole route. 
            
Suggestions
When both ends use the manual setting, the one-link failure will cause that one end is up and the other down, resulting in static black hole route. This may bring in severe failure. Therefore, it is recommended to use auto-negotiation mode (the precondition is that devices at both ends can work well in auto-negotiation mode). 
            

END